Beam defining apparatus



April 6, 1954 J. DANFORTH ET AL 2,674,698 BEAM DEFINING APPARATUS Filed July 2, 1952 5 Sheets-Sheet l HIGH ENERGY BEAM SOURCE ZSnventor JOHN L DAA/Fd/FTH LLOYD (P. Mam/705W Gttorneg April 6, 1954 J. DANFORTH ET AL 2,574,693

BEAM DEFINING APPARATUS Filed July 2, 1952 3 Sheets-Sheet 2 FIG. 3.

Zhmcntor (IO/IN L. DA/VFORTH 69 LLOYD E. Mam/7'05 April 6, 1954 J. DANFORTH ET AL 2,674,698

BEAM DEFINING APPARATUS Filed July 2, 1952 5 Sheets-Sheet 3 FIG. 4.

3nncutor JOHN L. BAA/FORTH LLOYD R. Mc/IVTOSH (Ittomeg Patented Apr. 6, 1954 BEAM DEFINING APPARATUS John- In Danforth; Westwod,.. and Lloyd R; Mc-

In'tosh, Winchester, Mass-,assignors, by mesne assignments, to the' United States of America as rcm'esented by the United States Atomic Energy Commission Apblication lilly -z'l- 1952, -Serlal N0. -296 ,966

5 Claims; 1

The present invention:- relates to a unitary beam defining" apparatus for: observing, control ling and measuring a beam of high: energy, charged atomic particles in a vacuum preparatory to using said defined beam-upon a: target. High energybeam sources: are now" being: con structed and uSedJinmany parts. of the: world; These sources are primarily utilized. for bornb'ardinga suitable target with -ahighenergy beam of charged atomic particles to produce and study nuclear reactions.

The construction: of. such a high energy; par ticle accelerator" represents a: large financial: unL- dertakingan'd once'the a'ccelerator.hasLbeenbuilt; it is common practice tomakeuse of it twentyfour hours a day whercpossiblez Ordinarymaintenance down time and the setup time between experiments are=the primary factors.- decreasing the productive capacity of the machine. Therefore, any improvementin an accelerator'which will permit the outputbeam thereof to be: de; fined rapidly as to location; shape and intensity in order to accommodate-it to difierent typeaof experiments will increasettl'ieproductive capacity of the machine by decreasing the experimental setup time.

Also today some positive-don: accelerators; such-as the well-known Vande Graafi' generator; are used as an initiaLsourcefoif a= higher-energy accelerator, such as the .protcn synchrotron,-. The Van de Graafi generator prov-idesa proton b'eam in the order oi twomillion electron volts: which will be accelerated in the proton synchrotron chamber up to en'ergiesapproaching three"- bile lion electron volts. When used'in'this Way; it is necessary that-the outputbeamof the Van de Graaif accelerator be accurately focused tit enterthe: proton synchrotron chamber at there quired position Prior art: devices have been built to carry out the beam defining function but they do not permit-simultaneous operation of the-various elements. Alsoeachottheelements is not Y as maneuverable-astheelementswf the present invention.

Itis accordinglyan object of the-presenb in vention to provide a" new and improvedbeam defining apparatus including collimatih'g 'm'eans and I adapted for use in the evacuated output tube of a high energy particle accelerator:

A second object of the present inventionis to provide a new and improved high" energy beam definingapparatus which includes means for viewing the high energy beam as wellam means for measuring the beam:

Still another obiect is to provide a new and improved unitary beam defining apparatus for use in the evacuated output tube of a high energyparticle accelerator andwhich can be-easily adjusted without affecting the high vacuum present in. the output tube.

More particularly; the apparatus is adapted for use in the evacuated output tube of a high energy particle accelerator and includes at hermetically scalable mounting block containing a bore through which the high energy beam is transmitted, reciprocally movable means mounted on the block and communicating with said bore for shaping. the beamas it passes therethrough, reciprocally movable means mounted on said block in communication withsaid. bore for viewing, the shaped beam, means mountedon said block. in communication with said bore for measuring the intensity'of the shaped beam and reciprocally movable into and out-oi the path of said beam and separate means sealing, each of said reciprocating meansin order to maintain a common vacuum inthe apparatus.

The many objects and advantages of the presentinvention may best be appreciated by reference to the accompanying. drawings, thefigures of which illustrate apparatus incorporating a preferred embodiment of the present invemtion and capable of carrying out the method of the invention. In the drawings:

Figure Lisa. schematic-representation of. the apparatus shown in its relationship to-the high energy beam source-and: output tube.

Figure 2 is a perspective view of a preferred embodiment. of. the apparatus.

Figure 3 isa transverse sectional. view taken alongthe lined-*3 of Figure 2.

Figure 4 is atransverse sectional viewtaken along. the lined-4 of Figure'2.

Referring to Figure 1, theunitary beam defining means I0 is diagrammatically shown mounted on theoutput, tube I I of a high-energy beam source I 2-; Connected to the oppo'site'side of the assembly Illis an evacuated'tube 13 for transmittingthe beam to the target I4. Also con-- nected to'the'a'ssembly H] by means of conduit I6 is a compressed air source I! and further connectedito the assembly 10" is a-microammeter l8 as by means of conductors [Band 2E1. Attached to thebeamsource l2 is-a vacuum line 21- connected to vacuum pumps -22 and 23 intandem. Pumps: 2 2-and:23 maybe-used -for evacuatingthe beam source [2, output tubes I l and I 3'; theas"- sembly I 0. andztlie' clmmber: including the target l4: mcroammeter lwandicompressed ain souroe plurality of spaced cylinders formed therein and adapted to receive sealed pistons movable within removable flange inserts suitaibly amxed in sealed relation upon the mounting block 25. Two pairs of oppositely disposed inserts are provided to mount suitable means for collimating the beam, another insert is provided to mount a. viewing means and still another insert is provided to mount a collecting means. As will be apparent, it is essential that suitable adjustment of the several means be provided without leakage into the evacuated system, and that means for carrying away heat be established. In normal operation, the mounting block 25 is hermetically sealed to the output tube I i of the high energy beam source i2 and to the tube i3 leading to the target so that the beam is transmitted in the direction indicated by the arrow 25.

Referring now to Figures 2 and 3, it will be noted that the beam collimating portion of the beam defining assembly comprises two pairs of oppositely disposed pistons extending into bore 24 and adapted to support adjustably the beam collimating clipping plates. In Figure 3 two such pistons 28 and 29 are shown, conveniently called the vertical pair although the invention is in no way limited to any particular angular disposition of the same.

Considering first the upper piston assembly which is typical of each of the three companion piston assemblies in the collimating portion, there is provided a cylinder wall insert having a fiange 3| and with one or more seals 32 and 33 between the inserts and the external wall or block 25. Adapted for slow movement within the insert is a hollow stepped piston 28 having at its outer end a hollow piston head 34 and at its inner end a suitably afiixed beam clipping plate 36 of an appropriate material such as tantalum.

Sealing means 31 and 38 may be provided between the piston and the cylinder insert.

Accordingly, when installed within the operating system, both the cylinder insert and the F stepped piston are fully held by the pressure differential in the position as shown. Suitable bolts or other means are provided, however, to hold the flanged insert 3| in desired position upon the mounting block. From the flange a slotted bracket 39 extends and by means of a suitable pin rigidly affixed to the piston and engaging in the slot, rotation between the piston and the bracket may be prevented while longitudinal movement therebetween is effected.

For adjusting the position of clipping plate there is provided a manually operable nut 45 contacting the surface of a laterally extending ledge 42 on the bracket and engaging a threaded rod 43 rigidly afiixed to piston head 34. Suitable flexible conduits, not shown, may be attached to a first connection 44 leading into the interior of the piston head 34 and to a second connection 46 leading from the hollow space within piston 28 thereby to circulate a suitable cooling medium while the apparatus is being subjected to the heating effect caused by the beam from the accelerator.

similarly, the lower piston 29 of the vertical pair has a suitably aflixed beam clipping plate 41 at its inner end. Plate 36 is shown to be substantially parallel to plate 41 in Figure 3, but this configuration is not essential for the proper carrying out of the invention. A horizontal pair" of oppositely disposed pistons is also mounted on the block 25 adapted for reciprocal movement into and out of the path of the high energy beam. The inner end of one piston 48 of the horizontal pair, together with its beam clipping plate 49, may be seen in Figure 3. The horizontal pistons may be mounted in the manner hereinabove described with respect to piston 28.

In operation, the beam coming in the direction of the arrow 25 may be intercepted by clipping plates 35 and 4'! to properly limit and shape the beam in the vertical dimension. Also, the horizontal pistons may be inserted or withdrawn to properly shape the beam in the horizontal direction. In order to properly shape the beam, however, it is necessary that some means for viewing and measuring the shaped beam be provided during the beam defining process.

Referring now to Figures 2 and 4, it will be noted that the beam viewing portion of the beam defining assembly comprises a hollow stepped piston 51 and an oppositely disposed transparent window 52. At the inner end of piston 5i is an inclined surface 53 containing a luminescent material 54 suitably afixed thereto. At the outer end, piston 5| has a hollow piston head 56 connected to a handle 5'1. Piston 51 is mounted in a manner similar to that described above for piston 28 and independent communication to the cooling medium may be made by suitable connectors 5B and 5t. Opposite inclined surface 53 is shown the transparent window 52 mounted on a fiange 6!.

In operating, the piston 5| may be inserted so that the luminescent material 54 is in the path of the high energy beam. The impingement of the beam will cause the material 54 to fluoresce and properly outline the shape of the beam. With a high energy beam, material 54 will become incandescent due to the local heating. This emission of light in the visible range may be viewed through window 52. A material that has been found suitable is Vycor, a quartz made by the Corning Glass Works, Corning, New York, and containing 98% silica. This material may also be used for window 52.

Therefore, with the above-described piston assemblies of the beam defining apparatus, it is possible to obtain a beam shaped in two dimensions. However, for most experimental setups, it is also necessary to know the intensity of the beam to be used as well as its shape and location.

Referring again to Figures 2 and 3, it can be seen that the collecting piston 62 is mounted in a cylindrical wall insert having a flange 63. At its inner end, piston 62 has a cup-shaped er:- tension 64, at the bottom of which is an electrically conductive plate 56. At its outer end, piston 82 has a hollow piston head 6'! which is connected to a reciprocally movable plunger 56 mounted within a cylinder 69. Communicating with the interior of cylinder 89 is an external fluid connection H. Communicating with the interior of the hollow stepped piston 62 and the hollow piston head 61 are fluid connections 12 and I3, respectively.

In operation, a flexible conduit may be attachedto a connection H from a conventional compressed air source and the application of the compressed air causes the plunger 38 to force the piston 6,2,into the bore 24 of the block 25.

Thc cup-shaped extension 6.3" intercepts thebeam 26* which impingesupon the electrically conducti ve plate 66. The'high energy beam imparts a charge tothe conductive plate 66- whi'ch charge can be measured by asuitable, conventional microammeter 18 connected between the piston 62 and ground. Since the collecting portion of the beam defining apparatus may be operated: by compressed air, it maybe remotely operated and the microammeter may also be. remotely connected. Similarly, the interior'of cylinder 69' may be connected to-a vacuum pump, notshown, tcv remove the compressed air in the cylinder, thereby remotely returning plunger 68' to the position shown in Figure 3. Therefore, thebeam emerging from the" high energy beam particle accelerator may be properly defined by use of the beam defining apparatus herein described.

In use, the mounting block is attached to the output tube of the accelerator and the interior thereof is. evacuated. by the same evacuating means used for the particle accelerator. When the accelerator is ready for use, the four reciprocally movable pistons of the beam collimating portion of the beam defining. assembly are fully inserted as is the beam viewing piston 5|. The collecting piston 62 of the beam defining assembly is withdrawn. The vertical pair of beam collimating pistons 28 and 29 is slowly withdrawn until the proper vertical dimension is obtained as seen on the luminescent material 54. Then the horizontal pair" of beam collimating elements of the beam defining apparatus is withdrawn :until the desired horizontal dimension is obtained.

To determine whether the beam as shaped is providing the proper intensity, the beam viewing piston 5| is withdrawn and the beam collecting piston 62 inserted. Since the collecting cup is electrically insulated from the grounded mounting block 25, it is possible to provide more accurate current readings by applying a positive bias voltage in the order of 50 to 100 volts to the cup. This will prevent high current readings due to secondary electrons being knocked off by the impact of the high energy beam. If the beam is of the desired intensity, as measured on the microammeter, piston 62 is withdrawn. The beam is now properly defined as to its location,

shape and intensity according to the desired 0 experimental setup for which it is to be used.

It is apparent that the beam may be shaped to have a circular or rectangular cross-section by using properly shaped beam clipping plates. Also, if any of the elements of the beam defining apparatus have tobe repaired or replaced when not in use, it can be quickly dismounted and a mounting flange such as the flange 74 shown in Figure 2 inserted. In this manner, the removed element can be repaired without further disturbing the evacuated parts of the accelerator.

While the salient features of this invention have been described with respect to one embodiment, it will of course be apparent that numerous modifications may be made within the spirit and scope of this invention and it is, therefore, not desired to limit the invention to the exact details shown except in so far as they may be defined in the following claims.

We claim:

1. Beam defining apparatus for use in the evacuated output tube of a high energy particle accelerator which comprises in combination a hermetically sealable mounting block having a bore therein through which the high energy beam is transmitted, reciprocally movable: collimating: means mounted on said block and communicate i'ng withsaid bore, said collimating means-includiing independently movable elements-for shaping; the beam in either'of two directions as it passes. therethrough, means mounted ons-aid; block in. communication with said bore and reciprocally movable for viewing the shaped beam, means mounted on said block incon'lmunicati'on with said bore for measuring the intensity of the. shaped beam and" reciprocally movable into and out of the'path' of said-shapedbeamand separate meanssealing each of said reciprocating means in order to-maintain a common vacuum insai'd apparatus.

2. Beam defining apparatus for use in the evacuated output tube of a high energy particle accelerator which comprises in combination a hermetically sealable mounting block having a bore therein through'which the high energy beam. is transmitted, a fi'rstpair of reciprocally movable beamshaping elements mounted on said block: diametrically disposed about said bore, each of. said elements having a plate at one end for intercepting'saidbeam, at second pair ofre'cipro cally' movable beamshaping elements mounted on said block diametrically disposed about said bore and perpendicular to said first pair, each of said second elements having a plate at one end for intercepting said beam, all of said plates being substantially parallel to one another, means mounted on said block in communication with said bore and reciprocally movable for viewing the shaped beam, means mounted on said block in communication with said bore for measuring the intensity of the shaped beam and reci rocally movable into and out of the path of said beam and separate means sealing each of said reciprocating means in order to maintain a common vacuum in said apparatus.

3. Beam defining apparatus for use in the evacuated output tube of a high energy particle accelerator which comprises in combination a hermetically sealable mounting block having a bore therein through which the high energy beam is transmitted, reciprocally movable collimating means mounted on said block and communicating with said bore for shaping the beam in either of two directions as it passes through the block, means mounted on said block in communication with said bore and reciprocally movable for viewing the shaped beam, a reciprocally movable element mounted on said block in communication with said bore for measuring the intensity of said beam, said element having a cup shaped extension for projection into and out of the path of said shaped beam, said cup shaped extension including an electrically conductive plate insulated from ground, means for measuring any difi'erence in potential between said conductive plate and ground and separate means sealing each of said reciprocating means in order to maintain a common vacuum in said apparatus.

4. Beam defining apparatus for use in the evacuated output tube of a high energy particle accelerator which comprises in combination a hermetically sealable. mounting block having a bore therein through which the high energy beam is transmitted, reciprocally movable collimating means mounted on said block and communicating with said bore for shaping the beam in either of two directions as it passes through the block, means mounted on said block in communication with said bore and reciprocally movable for viewing the beam, a water cooled reciprocally movable element mounted on said block in communication with said bore and adapted for remote operation for measuring the intensity of said beam, said element having a cup shaped extension for projection into and out of the path of said beam, said cup shaped extension including a tantalum plate insulated from ground, means for measuring any difference in potential between said tantalum plate and ground and separate means sealing each of said reciprocating means in order to maintain a common vacuum in said apparatus.

5. Beam defining apparatus for use in the evacuated output tube of a high energy particle accelerator which comprises in combination a hermetically scalable mounting block having a bore therein through which the high energy beam is transmitted, a first pair of cylindrical water cooled reciprocally movable beam shaping elements mounted on said block diametrically disposed about said bore and communicating therewith, each of said elements having a tantalum plate at one end for intercepting said beam, a second pair of cylindrical water cooled reciprocally movable beam shaping elements mounted on said block diametrically disposed about said bore and communicating therewith, said second pair of elements being perpendicular to said first pair and having a tantalum plate at one end of each element for intercepting said beam, all of said plates being substantially parallel to one another and electrically insulated from the mounting block, a reciprocally movable element mounted on said block in communication with said bore and having one surface thereof inclined to the path of said beam, a luminescent material mounted on said inclined surface, a transparent window mounted on said block diametrically opposite said inclined surface, means mounted on said block in communication with said bore for measuring the intensity of the beam and reciprocally movable into and out of the path of said shaped beam and separate means sealing each of said reciprocating means in order to maintain a common vacuum in said apparatus.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,361,722 Von Ardeene Oct. 31, 1944 2,448,594 Hillier et a1 Sept. '7, 1948 2,595,550 Simpson, Jr May 6, 1952 

